1. Field of the Invention
The present invention relates generally to a device for monitoring vital body movements and more particularly to a device for detecting episodes of apnea in infants.
2. Description of the Prior Art
In recent years, progress has been made in diagnosing the so-called "crib death" problem in which infants have died during sleep. It has been found that a significant percentage of infants up to the age of about one year may have problems in the involuntary breathing system such that, during sleep, respiration may cause, a condition often referred to as apnea. In most instances, the infant will begin breathing again spontaneously. However, if the duration of an apnea episode is excessive, irreversible cerebral damage may be sustained, and in some cases death occurs. Methods have been devised to determine which infants may have this problem.
When this condition is determined for an infant, it is necessary that the parents have a means for detecting the onset of an episode so that the infant may be assisted in restarting breathing. Although a number of efficient devices have been developed for use in hospitals for premature infants as well as other patients to monitor and produce an alarm when normal breathing stops, the cost and complexity of such devices precludes the average family from their use. Some units have been developed which are better adapted to home use but still suffer from problems of high cost and often from tendency to false alarms. Therefore, there is a need for a highly reliable and low cost unit that will be within the reach of even low income families.
Various types of apnea monitoring devices are described in the following patent Nos.:
3,875,929 Grant; PA1 3,926,177 Hardway et al.; PA1 3,727,606 Sielaff; PA1 3,942,513 Frank; PA1 3,903,876 Harris.
Grant teaches a microwave scanner which provides a movement sensitive field. However, the expense of providing what amounts to a radar transmitter and receiver contributes to an undesired high cost. In the patent to Hardway et al., a capacity pad or mattress is used in which the body lying on it will cause capacity variations with movement. A complex capacitance measuring circuit is required and a capacitive rate change measuring circuit is used. Sielaff teaches a fluid type mattress connected to a pressure transducer for measuring the variations in pressure with breathing and other movements. An extremely sensitive transducer must be used since the breathing of an infant would produce very minute variations in pressure. In the Frank patent, a closed loop monitor and stimulator is taught which uses a sensor attached to the patient and a stimulator which is energized when lack of breathing is sensed. The stimulator must be maintained in proper contact with the infant and requires a pneumatic supply unit for its operation. Harris discloses a monitor which is primarily used with a tracheostomy tube.
None of the known prior art apnea monitoring devices appear practical for low cost production for home use.